The present disclosure relates generally to information handling systems (IHS's), and more particularly to information handling systems which feature reduced power consumption.
As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
As power conservation is an ever present issue, many modern IHS's are designed with power savings features. A common method used in IHS's to achieve lower power usage is to configure IHS's and components with multiple power states. For example, according to the current Advanced Configuration and Power Interface (ACPI) standard, a typical IHS may enter into power savings states ranging from S0 (full on) to S4 (hibernate). More relevant to this disclosure, Intel Architecture based processors may operate in various power savings states known as “C states”, ranging from C0 (full power-least power saving state) to C4 (highest power saving state). Because “C States” higher than C2 present significantly greater power savings, it would be desirable for processors to operate in C3 and higher states whenever possible.
IHS's which feature bus mastering components present significant hurdles to achieving C3 and higher power savings states because any bus mastering activity prevents processors from entering C3 and higher states. One example of a type of component which utilizes bus mastering is a Universal Serial Bus (USB) component. USB component's prevalence in modern IHS's presents an acute challenge in designing more power efficient IHS's.
Some existing USB devices support power savings states through what is known as “selective-suspend.” “Selective-suspend” allows USB hubs to be suspended if no devices are connected to the hub. In addition, if only suspended USB devices are connected to a USB controller, the controller may also be suspended. Therefore, IHS's equipped with only “selective-suspend” compliant USB devices may operate with their processors in C3 and higher states. However, many USB devices do not support “selective-suspend.” This is especially true for USB storage devices.
Therefore, what is needed is a technique for enabling an IHS equipped with a bus mastering device, such as a non selective-suspend compliant USB device, to operate with its processor in enhanced power savings states such as C3 and higher states to reduce power consumption.